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compounds   (bromoform,   bromocarbonates).    Its   analysis   includes   the
following tests :

1.  Fixed Residue.—A few grams of bromine are allowed to volatilise
in a porcelain dish ;  pure bromine leaves no weighable residue.

2.  Organic Substances.—A few grams are dissolved in water and
excess of ammonia added ;   in presence of organic bromine compounds, a
turbid solution is obtained from which oily drops may separate.

3.  Sulphuric  Acid.—Part of the preceding arnmoniacal solution is
acidified with hydrochloric acid and tested with barium chloride.

4.  Iodine.—Another part of the arnmoniacal solution is evaporated
to dryness and the residue redissolved in water and treated with a few
drops of ferric chloride solution ; in presence of iodine, the liquid is coloured
yellow and gives a violet colour to carbon disulphide when shaken with this.

5.  Chlorine.—Another part of the arnmoniacal solution is evaporated
to dryness, o-i gram of the residue being dissolved in 10 c.c. of water and
4 c.c. of ammonium carbonate solution (i part of the carbonate, i part of
ammonia of D 0-96 and 3 parts of water) ;   12 c.c. of N/io-silver nitrate
are then added, and the liquid heated for a short time to 50-60° and filtered,
the nitrate being acidised with nitric acid.    With pure bromine, the liquid
is scarcely milky, but if chlorine is present a precipitate of silver chloride
is formed.

For a rapid determination, which is sufficiently exact, Kubierschki's
method 1 may be used.

Commercial bromine is generally pure ; that of the Stassfurt-Leopoldshall
Mining Syndicate is guaranteed to contain less than 0-3% of chlorine.

Ca(C2H302) 2 = 158-15

The pure salt is put on the market in colourless crystals extremely
soluble in water, but is of limited application ; the crude salt (calcium
pyrolignite), in brownish-grey, hygroscopic lumps or coarse powder with
a marked empyreurnatic odour, is an important raw material for the manu-
facture of acetic acid and other acetates. This crude salt is always con-
taminated with tarry substances, and also contains small quantities of
formate, propionate and other organic salts of calcium, calcium carbonate,
alumina, ferric oxide, etc. ; its value depends on its content of pure calcium
acetate or acetic acid, so that importance attaches to the quantitative
determination of the acid.

Determination of the Acetic Acid.—Use is made of a tubulated
retort of 200 c.c. capacity placed on a sand-bath, the neck being turned
up a little and connected with a condenser by means of an obtuse-angled
tube. In this, 5 grams of the acetate, 50 c.c. of water and 50 c.c. of ordinary
phosphoric acid (D = 1-20) free from nitric acid are heated and distilled
almost to dryness, the liquid being collected in a 250 c.c. n.easuring-flask;
after cooling, the retort is charged with another 50 c.c. of water and dis-
tillation almost to dryness repeated. At the end of the distillation, the
1 See Post, Chem.-techn. Analyse.ter